Oregon voters are poised to legalize same-sex marriage by amending the state Constitution for the second time in a decade, according to a new survey released this week.

The poll, conducted by Portland-based DHM Research, shows 58 percent of Oregon voters would back changing the state Constitution to allow marriage between homosexual couples.

That’s a sea change from 2004, when Oregon voters passed a constitutional amendment defining marriage as a union between one man and one woman by a 57 percent to 43 percent margin. That year, only two counties — Multnomah, home of Portland, and Benton, home of Corvallis and Oregon State University — voted against the ban.

If the ballot measure passes, Oregon would be the first and only state to have voted for a constitutional ban, and then to change the Constitution again to reverse that ban. Voters in Washington, Maine and Maryland overturned bans on same-sex marriage in 2012, but those were statutory bans not written into state constitutions.

Support for the ballot measure is broad: 44 percent told DHM pollsters they strongly support changing the Constitution, and more than two thirds of Democrats and 61 percent of independents said they would vote for the measure. About three in ten Republicans also said they would support changing the Constitution.

But Oregonians might not get the opportunity to vote on marriage equality at all. A lawsuit challenging the legality of the state’s ban on same-sex marriage is scheduled for oral arguments May 14 before U.S. District Court Judge Michael McShane.

Federal judges in Texas, Michigan, Utah, Virginia and Oklahoma have struck down similar statewide bans on same-sex marriage in recent months after the U.S. Supreme Court ruled last year that a California ban on gay marriage violated the U.S. Constitution.

The poll also showed Gov. John Kitzhaber (D) could be vulnerable to a strong challenge. Just 35 percent of voters say he deserves reelection, while 49 percent say it’s time to replace the three-term governor. But Republicans don’t have a great candidate to run against him: Kitzhaber leads state Rep. Dennis Richardson (R) by a 48 percent to 36 percent margin.

A majority of voters, 53 percent, say they approve of Kitzhaber’s job performance. Only 42 percent say they approve of the job Sen. Jeff Merkley (D) is doing, but a whopping 38 percent said they had no opinion; 20 percent disapproved of the job Merkley is doing.

And Oregon teachers apparently need to do a better job in civics class: Just 53 percent of Oregon voters knew how many U.S. Senators represent the state in Washington. Forty-one percent of high-frequency voters, those who cast ballots in three of the last four elections, couldn’t name the three branches of government.

The poll surveyed 400 registered Oregon voters for a margin of error of plus or minus 4.9 percent.